/*
 *  X.509 certificate writing
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 *
 *  This file is provided under the Apache License 2.0, or the
 *  GNU General Public License v2.0 or later.
 *
 *  **********
 *  Apache License 2.0:
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  **********
 *
 *  **********
 *  GNU General Public License v2.0 or later:
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  **********
 */
/*
 * References:
 * - certificates: RFC 5280, updated by RFC 6818
 * - CSRs: PKCS#10 v1.7 aka RFC 2986
 * - attributes: PKCS#9 v2.0 aka RFC 2985
 */

#if !defined(MBEDTLS_CONFIG_FILE)
#include "nettls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_X509_CRT_WRITE_C)

#include "nettls/x509_crt.h"
#include "nettls/oid.h"
#include "nettls/asn1write.h"
#include "nettls/sha1.h"
#include "nettls/platform_util.h"

#include <string.h>

#if defined(MBEDTLS_PEM_WRITE_C)
#include "nettls/pem.h"
#endif /* MBEDTLS_PEM_WRITE_C */

/*
 * For the currently used signature algorithms the buffer to store any signature
 * must be at least of size MAX(MBEDTLS_ECDSA_MAX_LEN, MBEDTLS_MPI_MAX_SIZE)
 */
#if MBEDTLS_ECDSA_MAX_LEN > MBEDTLS_MPI_MAX_SIZE
#define SIGNATURE_MAX_SIZE MBEDTLS_ECDSA_MAX_LEN
#else
#define SIGNATURE_MAX_SIZE MBEDTLS_MPI_MAX_SIZE
#endif

void mbedtls_x509write_crt_init(mbedtls_x509write_cert* ctx)
{
    memset(ctx, 0, sizeof(mbedtls_x509write_cert));

    mbedtls_mpi_init(&ctx->serial);
    ctx->version = MBEDTLS_X509_CRT_VERSION_3;
}

void mbedtls_x509write_crt_free(mbedtls_x509write_cert* ctx)
{
    mbedtls_mpi_free(&ctx->serial);

    mbedtls_asn1_free_named_data_list(&ctx->subject);
    mbedtls_asn1_free_named_data_list(&ctx->issuer);
    mbedtls_asn1_free_named_data_list(&ctx->extensions);

    mbedtls_platform_zeroize(ctx, sizeof(mbedtls_x509write_cert));
}

void mbedtls_x509write_crt_set_version(mbedtls_x509write_cert* ctx, int version)
{
    ctx->version = version;
}

void mbedtls_x509write_crt_set_md_alg(mbedtls_x509write_cert* ctx, mbedtls_md_type_t md_alg)
{
    ctx->md_alg = md_alg;
}

void mbedtls_x509write_crt_set_subject_key(mbedtls_x509write_cert* ctx, mbedtls_pk_context* key)
{
    ctx->subject_key = key;
}

void mbedtls_x509write_crt_set_issuer_key(mbedtls_x509write_cert* ctx, mbedtls_pk_context* key)
{
    ctx->issuer_key = key;
}

int mbedtls_x509write_crt_set_subject_name(mbedtls_x509write_cert* ctx, const char* subject_name)
{
    return mbedtls_x509_string_to_names(&ctx->subject, subject_name);
}

int mbedtls_x509write_crt_set_issuer_name(mbedtls_x509write_cert* ctx, const char* issuer_name)
{
    return mbedtls_x509_string_to_names(&ctx->issuer, issuer_name);
}

int mbedtls_x509write_crt_set_serial(mbedtls_x509write_cert* ctx, const mbedtls_mpi* serial)
{
    int ret;

    if ((ret = mbedtls_mpi_copy(&ctx->serial, serial)) != 0)
        return (ret);

    return (0);
}

int mbedtls_x509write_crt_set_validity(mbedtls_x509write_cert* ctx, const char* not_before, const char* not_after)
{
    if (strlen(not_before) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1 || strlen(not_after) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1) {
        return (MBEDTLS_ERR_X509_BAD_INPUT_DATA);
    }
    strncpy(ctx->not_before, not_before, MBEDTLS_X509_RFC5280_UTC_TIME_LEN);
    strncpy(ctx->not_after, not_after, MBEDTLS_X509_RFC5280_UTC_TIME_LEN);
    ctx->not_before[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';
    ctx->not_after[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';

    return (0);
}

int mbedtls_x509write_crt_set_extension(
    mbedtls_x509write_cert* ctx, const char* oid, size_t oid_len, int critical, const unsigned char* val, size_t val_len)
{
    return (mbedtls_x509_set_extension(&ctx->extensions, oid, oid_len, critical, val, val_len));
}

int mbedtls_x509write_crt_set_basic_constraints(mbedtls_x509write_cert* ctx, int is_ca, int max_pathlen)
{
    int ret;
    unsigned char buf[9];
    unsigned char* c = buf + sizeof(buf);
    size_t len = 0;

    memset(buf, 0, sizeof(buf));

    if (is_ca && max_pathlen > 127)
        return (MBEDTLS_ERR_X509_BAD_INPUT_DATA);

    if (is_ca) {
        if (max_pathlen >= 0) {
            MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, max_pathlen));
        }
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_bool(&c, buf, 1));
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    return (mbedtls_x509write_crt_set_extension(
        ctx, MBEDTLS_OID_BASIC_CONSTRAINTS, MBEDTLS_OID_SIZE(MBEDTLS_OID_BASIC_CONSTRAINTS), 0, buf + sizeof(buf) - len, len));
}

#if defined(MBEDTLS_SHA1_C)
int mbedtls_x509write_crt_set_subject_key_identifier(mbedtls_x509write_cert* ctx)
{
    int ret;
    unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */
    unsigned char* c = buf + sizeof(buf);
    size_t len = 0;

    memset(buf, 0, sizeof(buf));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_pk_write_pubkey(&c, buf, ctx->subject_key));

    ret = mbedtls_sha1_ret(buf + sizeof(buf) - len, len, buf + sizeof(buf) - 20);
    if (ret != 0)
        return (ret);
    c = buf + sizeof(buf) - 20;
    len = 20;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_OCTET_STRING));

    return mbedtls_x509write_crt_set_extension(
        ctx, MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER, MBEDTLS_OID_SIZE(MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER), 0, buf + sizeof(buf) - len, len);
}

int mbedtls_x509write_crt_set_authority_key_identifier(mbedtls_x509write_cert* ctx)
{
    int ret;
    unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */
    unsigned char* c = buf + sizeof(buf);
    size_t len = 0;

    memset(buf, 0, sizeof(buf));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_pk_write_pubkey(&c, buf, ctx->issuer_key));

    ret = mbedtls_sha1_ret(buf + sizeof(buf) - len, len, buf + sizeof(buf) - 20);
    if (ret != 0)
        return (ret);
    c = buf + sizeof(buf) - 20;
    len = 20;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC | 0));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    return mbedtls_x509write_crt_set_extension(
        ctx, MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER, MBEDTLS_OID_SIZE(MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER), 0, buf + sizeof(buf) - len, len);
}
#endif /* MBEDTLS_SHA1_C */

static size_t crt_get_unused_bits_for_named_bitstring(unsigned char bitstring, size_t bit_offset)
{
    size_t unused_bits;

    /* Count the unused bits removing trailing 0s */
    for (unused_bits = bit_offset; unused_bits < 8; unused_bits++)
        if (((bitstring >> unused_bits) & 0x1) != 0)
            break;

    return (unused_bits);
}

int mbedtls_x509write_crt_set_key_usage(mbedtls_x509write_cert* ctx, unsigned int key_usage)
{
    unsigned char buf[4], ku;
    unsigned char* c;
    int ret;
    size_t unused_bits;
    const unsigned int allowed_bits = MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT
                                      | MBEDTLS_X509_KU_DATA_ENCIPHERMENT | MBEDTLS_X509_KU_KEY_AGREEMENT | MBEDTLS_X509_KU_KEY_CERT_SIGN
                                      | MBEDTLS_X509_KU_CRL_SIGN;

    /* Check that nothing other than the allowed flags is set */
    if ((key_usage & ~allowed_bits) != 0)
        return (MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE);

    c = buf + 4;
    ku = (unsigned char)key_usage;
    unused_bits = crt_get_unused_bits_for_named_bitstring(ku, 1);
    ret = mbedtls_asn1_write_bitstring(&c, buf, &ku, 8 - unused_bits);

    if (ret < 0)
        return (ret);
    else if (ret < 3 || ret > 4)
        return (MBEDTLS_ERR_X509_INVALID_FORMAT);

    ret = mbedtls_x509write_crt_set_extension(ctx, MBEDTLS_OID_KEY_USAGE, MBEDTLS_OID_SIZE(MBEDTLS_OID_KEY_USAGE), 1, c, (size_t)ret);
    if (ret != 0)
        return (ret);

    return (0);
}

int mbedtls_x509write_crt_set_ns_cert_type(mbedtls_x509write_cert* ctx, unsigned char ns_cert_type)
{
    unsigned char buf[4];
    unsigned char* c;
    size_t unused_bits;
    int ret;

    c = buf + 4;

    unused_bits = crt_get_unused_bits_for_named_bitstring(ns_cert_type, 0);
    ret = mbedtls_asn1_write_bitstring(&c, buf, &ns_cert_type, 8 - unused_bits);
    if (ret < 3 || ret > 4)
        return (ret);

    ret = mbedtls_x509write_crt_set_extension(ctx, MBEDTLS_OID_NS_CERT_TYPE, MBEDTLS_OID_SIZE(MBEDTLS_OID_NS_CERT_TYPE), 0, c, (size_t)ret);
    if (ret != 0)
        return (ret);

    return (0);
}

static int x509_write_time(unsigned char** p, unsigned char* start, const char* t, size_t size)
{
    int ret;
    size_t len = 0;

    /*
     * write MBEDTLS_ASN1_UTC_TIME if year < 2050 (2 bytes shorter)
     */
    if (t[0] == '2' && t[1] == '0' && t[2] < '5') {
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, (const unsigned char*)t + 2, size - 2));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_UTC_TIME));
    } else {
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, (const unsigned char*)t, size));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_GENERALIZED_TIME));
    }

    return ((int)len);
}

int mbedtls_x509write_crt_der(mbedtls_x509write_cert* ctx, unsigned char* buf, size_t size, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng)
{
    int ret;
    const char* sig_oid;
    size_t sig_oid_len = 0;
    unsigned char *c, *c2;
    unsigned char hash[64];
    unsigned char sig[SIGNATURE_MAX_SIZE];
    size_t sub_len = 0, pub_len = 0, sig_and_oid_len = 0, sig_len;
    size_t len = 0;
    mbedtls_pk_type_t pk_alg;

    /*
     * Prepare data to be signed at the end of the target buffer
     */
    c = buf + size;

    /* Signature algorithm needed in TBS, and later for actual signature */

    /* There's no direct way of extracting a signature algorithm
     * (represented as an element of mbedtls_pk_type_t) from a PK instance. */
    if (mbedtls_pk_can_do(ctx->issuer_key, MBEDTLS_PK_RSA))
        pk_alg = MBEDTLS_PK_RSA;
    else if (mbedtls_pk_can_do(ctx->issuer_key, MBEDTLS_PK_ECDSA))
        pk_alg = MBEDTLS_PK_ECDSA;
    else
        return (MBEDTLS_ERR_X509_INVALID_ALG);

    if ((ret = mbedtls_oid_get_oid_by_sig_alg(pk_alg, ctx->md_alg, &sig_oid, &sig_oid_len)) != 0) {
        return (ret);
    }

    /*
     *  Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension
     */

    /* Only for v3 */
    if (ctx->version == MBEDTLS_X509_CRT_VERSION_3) {
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf, ctx->extensions));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 3));
    }

    /*
     *  SubjectPublicKeyInfo
     */
    MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->subject_key, buf, c - buf));
    c -= pub_len;
    len += pub_len;

    /*
     *  Subject  ::=  Name
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf, ctx->subject));

    /*
     *  Validity ::= SEQUENCE {
     *       notBefore      Time,
     *       notAfter       Time }
     */
    sub_len = 0;

    MBEDTLS_ASN1_CHK_ADD(sub_len, x509_write_time(&c, buf, ctx->not_after, MBEDTLS_X509_RFC5280_UTC_TIME_LEN));

    MBEDTLS_ASN1_CHK_ADD(sub_len, x509_write_time(&c, buf, ctx->not_before, MBEDTLS_X509_RFC5280_UTC_TIME_LEN));

    len += sub_len;
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, sub_len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    /*
     *  Issuer  ::=  Name
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf, ctx->issuer));

    /*
     *  Signature   ::=  AlgorithmIdentifier
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_algorithm_identifier(&c, buf, sig_oid, strlen(sig_oid), 0));

    /*
     *  Serial   ::=  INTEGER
     */
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_mpi(&c, buf, &ctx->serial));

    /*
     *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
     */

    /* Can be omitted for v1 */
    if (ctx->version != MBEDTLS_X509_CRT_VERSION_1) {
        sub_len = 0;
        MBEDTLS_ASN1_CHK_ADD(sub_len, mbedtls_asn1_write_int(&c, buf, ctx->version));
        len += sub_len;
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, sub_len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0));
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    /*
     * Make signature
     */

    /* Compute hash of CRT. */
    if ((ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash)) != 0) {
        return (ret);
    }

    if ((ret = mbedtls_pk_sign(ctx->issuer_key, ctx->md_alg, hash, 0, sig, &sig_len, f_rng, p_rng)) != 0) {
        return (ret);
    }

    /* Move CRT to the front of the buffer to have space
     * for the signature. */
    memmove(buf, c, len);
    c = buf + len;

    /* Add signature at the end of the buffer,
     * making sure that it doesn't underflow
     * into the CRT buffer. */
    c2 = buf + size;
    MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len, mbedtls_x509_write_sig(&c2, c, sig_oid, sig_oid_len, sig, sig_len));

    /*
     * Memory layout after this step:
     *
     * buf       c=buf+len                c2            buf+size
     * [CRT0,...,CRTn, UNUSED, ..., UNUSED, SIG0, ..., SIGm]
     */

    /* Move raw CRT to just before the signature. */
    c = c2 - len;
    memmove(c, buf, len);

    len += sig_and_oid_len;
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));

    return ((int)len);
}

#define PEM_BEGIN_CRT "-----BEGIN CERTIFICATE-----\n"
#define PEM_END_CRT   "-----END CERTIFICATE-----\n"

#if defined(MBEDTLS_PEM_WRITE_C)
int mbedtls_x509write_crt_pem(mbedtls_x509write_cert* crt, unsigned char* buf, size_t size, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng)
{
    int ret;
    size_t olen;

    if ((ret = mbedtls_x509write_crt_der(crt, buf, size, f_rng, p_rng)) < 0) {
        return (ret);
    }

    if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CRT, PEM_END_CRT, buf + size - ret, ret, buf, size, &olen)) != 0) {
        return (ret);
    }

    return (0);
}
#endif /* MBEDTLS_PEM_WRITE_C */

#endif /* MBEDTLS_X509_CRT_WRITE_C */
